When I started out scopes were seldom used in wooded country, and in open spaces 3 power were the standard and 4 powers were just coming into widespread availablity. Then came the varilable craze, not strictly necessary but handy a scope of 2-7 power with a 32 or 33 mm objective lens in adequate for just about every type of medium or big game hunting that exists in the U. S. Varmints, of course, are different, some are small and shot a very long ranges so the higher powers are quite helpful. As for the brightness one way to judge is by the exit pupil. It is easy to figure, and the formula doesn't change with the coatings used. Divide the size of the objective lens by the power the resultant is the size of the column of light that leaves the ocular lens. There is no need to have an exit pupil that is larger than the one of your own eye. Young folks will have pupils that are capable of expanding to 6 or so mm. Older folks can't get theirs open that far. A 4 power scope with a 32mm objective lens would have an exit pupil of 8mm, or more than anyone could take advantage of. The scopes with 50 mm objective lenses would be well suited to use in moonlight with relatively high magnification. Varmint hunting if you'd like to do it at night might require such a scope. In exchange your face is lifted off of the stock, and recoil of the rifle can smack you one in the cheek and make you wish you had a smaller scope. Additionally the scope would tend to tilt the entire rifle, or cant it. This can be detrimental to accuracy. In scopes, bigger is not always better.